It is desirable to verify the performance by radio and television broadcasters of advertisements. Advertisers purchasing broadcast time from radio and television stations are contractually obligated to pay for this time only if the advertisement was broadcast in accordance with the agreed terms and conditions. Generally these terms include a description of the advertisement to be broadcast, the time period in which it is to be broadcast, and certain obligations to replay the advertisement if parameters agreed to by the broadcaster and the purchaser of the broadcast time are not met by the broadcaster. The contractual compliance of performance from radio and television broadcasters previously has been attested to by sworn affidavits.
The current state of the art accomplishes independent verification primarily through human observation. Observers listen or watch for the advertisement and note the time and broadcasting radio or television station in a log record. Technical methods have also been employed. These require previous processing of the advertisement by pre-processing insertion of an identification code or digital watermark into the commercial material.
Principal among the technological techniques for marking broadcast content for performance verification are (1) insertion of a digital watermark into the video waveform or the audible portion of the transmitted audio spectrum, (2) insertion of data in under-utilized portions of the video waveform such as scan lines above or below the viewable area of the interleaved video frame, (3) insertion of data as sub-audible or super-audible tones or combinations of tones in the transmitted audio spectrum, or (4) insertion of identification codes as data utilizing either the frequency or phase domains.
All of these technical methods are nonintrusive. The techniques generally require the creation of a compressed representation, signature or digital fingerprint prior to the distribution of the radio or television commercial advertisement. The results of the broadcast performance on either radio or television of the previously compressed content can be matched by the application of an identical data compression technique at the time the broadcast commercial is received.
Digital watermarks are effective in applications such as digital rights management for compact discs (CDs) and digital video discs (DVDs) where the attribution of the watermarked content is permanently identified with a single source such as a studio, publisher or performing artist, and multiple copies of the content are to be distributed. The digital watermark fails in efficacy where the identification, verification or authentication must be attributed to multiple sources such as the purchasers of broadcast radio or television advertising time that are not associated with the producer of the digital watermarked advertising content distributed to the broadcaster.
Digital watermarking systems for audio content such as U.S. Pat. No. 5,940,135 to Petrovic et al. (1999) generally employ techniques that in some way manipulate the content in either the phase, time or frequency domains, or any number of permutations of the three. These approaches are readily apparent to the accomplished and discerning listener. They appear to the accomplished listener as audible degradations of the audio content either as blurred edges to crisp, high frequency sonic colorations, as phase “pumping” or wavering in all frequencies whose coloration should appear steady to the discerning human ear.
Other identification systems known to the art rely on the insertion of digital data into the typically unseen scan lines that appear in the broadcast video frame above or below the normal viewing area of the television picture. These in-line insertion methods such as U.S. Pat. No. 4,025,851 to Hazelwood et al. (1977), U.S. Pat. Nos. 4,457,804; 4,639,779; 4,805,020 to Greenberg (1985-1989), U.S. Pat. No. 5,450,122 to Keane et al. (1995) generally use video scan line 20 as the location for the insertion of binary identification codes. These approaches are, like digital watermarks, generally effective when applied to network or other single source originations where there exists a one-to-one relationship between the television advertising content and the owner of the commercial or the advertising agency that originated the contract, or as is known in the broadcast industry as an “Insertion Order” that purchased the advertising time. These methodologies fail where the television commercial is broadly disseminated for use by purchasers of local or network advertising time other than the originator or its representative advertising agency.
Other systems have combined modulated data with the audio or video channel of the program segment using frequency shift keyed modulation (FSK) such as U.S. Pat. No. 5,128,933 Baranoff-Rossine (1992) or U.S. Pat. No. 5,663,766 Sizer, II (1997). Some of these systems have notched out sections of the audio channel within the range of human hearing and FSK-encoded data using audible frequencies with amplitudes that are substantially inaudible to the typical listener.
In one system known to the art, a subaudible (below the nominal frequency range of human hearing) frequency band was chosen to encode the identification data and on-off keying of a fixed modulation frequency was used to designate the binary data content. Such a system is believed to have an undesirable amount of noise susceptibility, because it is not possible to differentiate between the absence of a modulation frequency and an off-keyed modulation state.
Other identification methods known to the art use frequency spread spectrum techniques to periodically insert time-stamp and identification information into master audio recordings for the purpose of recovering this time and identification data for performance verification. U.S. Pat. No. 5,379,345 to Greenberg (1995) is one such example. This approach, like digital watermarking, while effective in identifying mass copies of advertising content, fails in efficacy where the encoded identification points to an individual or entity other than the purchaser of the radio or television broadcast advertising time seeking proof of performance.
A further problem with audio applications of the frequency spread spectrum method is that, in the absence of audio data carrier components to mask the code frequencies, they can become audible. This method, therefore, relies on the asserted noise-like character of the codes to suggest that their presence will be ignored by listeners. However, in the case of an accomplished listener this assumption may not be valid, for example, in the case of recorded music containing passages with relatively little audio carrier content or during pauses in speech.
Other forms of identification and verification rely on signatures, digital fingerprinting or other related pattern recognition techniques such as those described in U.S. Pat. Nos. 4,230,990 and 4,677,466 to Lert, Jr. et al. (1980, 1987) and U.S. Pat. No. 4,450,531 to Kenyon et al. (1984). These approaches require prior knowledge of the audio or video subject-matter content, which are not available in real-time. Also such comparison techniques are of only limited reliability due to normal degradation of the signal due to airborne broadcast transmission, such as electromagnetic interference, multi-path transmission errors, and a number of other environmental disturbances. These forms of pattern comparison of a portion of an audio or video content can be utilized for identification purposes, but the comparison requires significant analysis and has a high probability of inaccuracy.
Although systems such as those described above are typically sufficient for the particular and initial purposes for which they were designed, they suffer certain deficiencies inherent to their ubiquitous use for broadcast verification. Encoding methods and compressed identification techniques generally adopted in the broadcast industry fail to accurately attribute broadcast advertisements to the purchasers of the commercial time when the purchaser is not the originator of the encoding or the fingerprinting of the advertisement when it was created.